1. Field of the Invention
The present invention relates to a manual transmission for motor vehicles. More particularly, this invention relates to a shift rail mechanism in a multiple gear automotive manual transmission.
2. Description of the Prior Art
This invention comprises a manual transmission assembly having a shift rail and multiple gearing for use with an internal combustion vehicle engine. An example of a transmission presently known in the prior art is illustrated in U.S. Pat. No. 4,222,281 ('281), assigned to the assignee of the present application. In the '281 patent, the shifting mechanism comprises a single shift rail and shift lever assembly for actuating synchronizer clutch mechanisms, including a first motion reversing lever assembly establishing a connection between the single shift rail and the synchronizer clutch mechanism for third and fourth ratio changes and another lever assembly for reversing the motion imparted to a reverse drive pinion by the single shift rail; the reverse drive pinion being shiftable to a driving position or to an inoperative position and the synchronizer clutch mechanism for the first and second speed ratio changes including an integral main drive gear that forms a part of the reverse torque delivery path.
A second example of a single rail shift mechanism for a manual transmission is shown in U.S. Pat. No. 4,532,823 ('823), to Razzacki. In the '823 patent, the shift rail assembly has a single shift rod slidably received within an outer concentric tubular member. A first-second (1-2) speed fork is supported on the tubular member for movement therewith. A third-fourth (3-4) speed fork is slidably supported on the tubular shift rail for axial movement relative thereto. A fifth speed fork is fixedly retained on one free end of the shift rod. The tubular member has a pair of diametrically opposed elongated control slots receiving a transverse cross pin which extends from the fifth speed shifter through the tubular member and rod. Journal bearings are provided between the outer tubular member and the inner shift rod. This arrangement enables the 1-2 speed fork having the highest shifting resistance, to be readily shifted on the journalled tubular member in a predetermined manner reducing gear shift lever operating efforts.
The prior art single rail shift mechanisms provided several complex moving parts to enable gear selection. For example, the transmission of the '281 patent includes shift levers to effectuate gear selections. The transmission of the '823 patent requires relative movement of the shift rod, the tubular rail., and the 3-4 shift member to the tubular rail in order to effectuate shifts into 1, 3, or 5th gear. Additionally, the selector of the shift mechanism of the '823 patent has a finger which must engage the fork notches. It is unclear to applicant how this is accomplished in the '823 patent without alignment problems during operation of the '823 transmission. Finally, the '823 patent only teaches selection of 1st-5th gears.